Recently, an image display system, instead of a back mirror and a side mirror, of vehicles has been developed. In the image display system, an image obtained by imaging a rear of a vehicle by an imaging device is displayed on a monitor. A driver of the vehicle can recognize the situations on the rear of the center, the rear of the left, and the rear of the right of the vehicle by viewing a display of the monitor.
Further, as an example of a related art of the present disclosure, an imaging device is disclosed that detects a presence or an absence of a failure in a logic circuit that processes an image signal input from an imaging element. In such an imaging device, when a failure in the logic circuit is detected, the operation of the imaging device is stopped.
However, when an abnormal output from the imaging device occurs while the situation on the rear of the vehicle is viewed through the image of the monitor, there is a possibility that the driver of the vehicle may not drive the vehicle properly, causing an accident. For example, when a normal image signal is not input to the monitor, since the monitor cannot display an image of the rear of the vehicle, the driver cannot recognize the situation at the rear of the vehicle. In addition, when a portion of an imaging range of the imaging device is not imaged normally, a driver's visible range of display of the monitor is narrowed and the situation in the invisible range cannot be recognized. Moreover, when the imaging of the imaging device is stopped and the monitor can only display a still image before the stop of the imaging device, the driver may not know that the display of the monitor is a still image, and may not recognize that the imaging by the imaging device was stopped. In this case, the driver cannot recognize the situation at the rear of the vehicle and mistakenly recognizes the situation immediately before the imaging was stopped as the situation at the rear of the vehicle at the present time. This may lead to an accident resulting from misjudgment of the driver. In response to such problem, in the above related art, when power is turned on or off, only the presence or absence of a failure may be detected when invalid data of an image signal is output, and a configuration of the imaging device is complicated.